The present invention relates to a reduced-pressure syringe and its manufacturing method. More particularly, the invention relates to a reduced-pressure syringe for storing a freeze-dried agent therein under reduced pressure as well as a method for manufacturing the reduced-pressure syringe.
Conventionally, among freeze-dried agents, which are dissolved before use, some are unstable and prone to be decomposed with moisture, oxygen and the like, while others have a tendency that foams will not disappear at the dissolution. Such freeze-dried agents, including antibiotics, growth hormones and vaccines, are generally stored in a vial under reduced pressure, lower than atmospheric pressure, with a view to stable storage and prevention of foaming at dissolution. However, in one case where a chemical is stored in a vial, the chemical needs to be moved to a syringe after dissolved, not ready for instant use. In another case where a chemical resulting from dissolution of a freeze-dried agent has a high viscosity, the chemical is difficult to suck up. For these and other reasons, it is considered convenient to provide a prefilled syringe in which a freeze-dried agent is stored under reduced pressure.
Unfortunately, however, it has been impossible for conventional prefilled syringes to store a freeze-dried agent under reduced pressure.
More specifically, for sealing a freeze-dried agent into a syringe, generally, for example as shown in FIG. 1, a chemical 2 is injected into a cartridge 1 with its one sealed end down, and the cartridge 1 is plugged halfway on the other end side with a gasket 3. Then, while the cartridge 1 is held communicating between inside and outside through slit grooves 4 formed in the outer circumferential surface of lower part of the gasket 3, the chemical 2 is freeze-dried in a freeze dryer. That is, the chemical 2 is frozen and reduced in pressure so that its moisture is removed, by which a freeze-dried agent 2xe2x80x2 is formed.
Next, as shown in FIG. 2, with the reduced-pressure state held, the gasket 3 is pushed all the way into the syringe 1 by a shelf 5 of the freeze dryer so that the freeze-dried agent 2xe2x80x2 is sealed and accommodated in the syringe 1. Thereafter, as shown in FIG. 3, the syringe 1 is taken out from the freeze dryer and a cap 6 for packaging use is attached to the other end of the syringe 1. The syringe, when taken out from the reduced-pressure freeze dryer into atmospheric pressure, undergoes a pressure difference from atmospheric pressure due to the fact that interior of the gasket 3, i.e., interior of the cartridge 1 is in a reduced-pressure state. Therefore, the gasket 3 is further pushed into the syringe 1 by atmospheric pressure. As a result, the space in which the freeze-dried agent 2xe2x80x2 is sealed and accommodated goes smaller into a generally atmospheric-pressure state, thus making it impossible to store the freeze-dried agent 2xe2x80x2 under reduced pressure (for example, Japanese Patent Laid-Open Publication HEI 7-213608).
Accordingly, a technical object of the present invention is to provide a reduced-pressure syringe, as well as a manufacturing method therefor, for storing a freeze-dried agent under reduced pressure.
In order to achieve the above technical object, the present invention provides a reduced-pressure syringe having the following constitution.
The reduced-pressure syringe of the present invention is basically so structured that within a generally cylindrical-shaped cartridge having a pair of ends in which one of the ends is openably sealed, a gasket having a pair of end faces is slidably provided on a side of the other of the ends of the cartridge, thereby defining a sealed space, where a freeze-dried agent is accommodated in the sealed space, and in which the gasket has, in its outer circumferential surface, a recessed groove continuing from one of the end faces of the gasket on the side of the one of the ends of the cartridge toward the other of the end faces thereof on the side of the other of the ends thereof to an intermediate position therebetween. The syringe further comprises sealing cap which is to be engaged with an end face of the cartridge on the side of the other of the ends and which seals the side of the other threreof. A pressure in the sealed space is held lower than atmospheric pressure.
Preferably, the reduced-pressure syringe having the above constitution is manufactured by the following method.
That is, the syringe comprises: a generally cylindrical-shaped cartridge having a pairs of ends in which one of the ends is openably sealed; a gasket having a pair of end faces and having, in its outer circumferential surface, a recessed groove continuing from one of the end faces of the gasket toward the other of the end faces thereof to an intermediate position therebetween; and a sealing cap. The method for manufacturing the reduced-presseure syringe comprises first, second and third steps. In the first step, a specified amount of a chemical in injected into the cartridge with the one of the ends of the cartridge. In the second step, the gasket is inserted halfway on a side of the other of the ends of the cartridge, into which the chemical has been ted, with the recessed groove of the gasket down, so that the cartridge is made communicating between inside and outside through the recessed groove, and then the chemical placed within the cartridge is freeze-dried in a freeze-drying chamber under a reduced-pressure atmosphere. In the third step, the sealing cap is overlaid on upper one of the end faces of the gasket and pushing the sealing cap toward the cartridge side in the freeze-drying chamber under the reduced-pressure atmosphere so that the side of the other of the ends of the cartridge is sealed by the gasket and the sealing cap, and that the sealing cap is engaged with an end face of the cartridge on the side of the other of the ends thereof.
In this manufacturing method, by the second step, a freeze-dried agent is formed on the lower side, i.e. the side of the one of the ends, of the cartridge. By the third step, the gasket is pushed into the cartridge, so that the cartridge is sealed on both sides thereof, i.e. on the side of the one of the ends of the cartridge where the freeze-dried agent is formed (i.e., sealed space) and on the side of the other of the ends of the cartridge where the gasket and sealing cap are placed, respectively, under a pressure lower than atmospheric pressure. While the syringe is kept in the freeze-drying chamber, freeze-drying process and plugging process of the gasket and the sealing cap can be carried out continuously under a reduced-pressure atmosphere. Preferably, the freeze-drying and plugging processes are carried out with the sealing cap overlaid on the upper end face of the gasket.
The reduced-pressure syringe having the above constitution is sealed with its interior in a reduced-pressure state, for example, by the above manufacturing method. Even if this syringe is taken out from the freeze-drying chamber having a reduced-pressure atmosphere into atmospheric pressure, the sealing cap is never pushed into the cartridge of the reduced-pressure state by atmospheric pressure because the sealing cap is engaged with the end face of the cartridge on the side of the other of the ends so as to be inhibited from moving into the syringe. Thus, the sealed space, in which the freeze-dried agent is accommodated, is held in the reduced-pressure state. Furthermore, if a space is present between the sealing cap and the gasket, the space is also held in the reduced-pressure state.
Therefore, the freeze-dried agent can be stored in the syringe under reduced pressure.
Preferably, the gasket has a fitting hole for fitting a plunger rod to the other of the end faces of the gasket on the side of the other of the ends of the cartridge. The sealing cap has a positioning protrusion which is to be inserted into the fitting hole of the gasket, the positioning protrusion being provided in an end face of the sealing cap on the side of the one of the ends of the cartridge.
With this arrangement, by inserting the positioning protrusion of the sealing cap into the fitting hole of the gasket, the sealing cap can be overlaid and positioned on the end face of the gasket on the side of the other of the ends of the cartridge and this state can be held. Thus, the work of plugging the sealing cap with the sealing cap overlaid on the gasket and, at the same time, pushing the gasket into the cartridge becomes easily attainable.